TLP:WHITE

DEVELOPMENT OF THE
ACTIVITY OF THE TA505
CYBERCRIMINAL GROUP

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Table of contents
1 TA505 from 2014 to 2017 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.1 Malware distributed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.1.1 Banking trojans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.1.2 Ransomware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.2 Distribution and compromise methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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2 Development of TA505 since 2018 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.1 Infection vector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2 Social engineering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3 Initial compromise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3.1 Stage 1 codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3.2 Second-level codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.4 Compromising of the information system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.4.1 Exploration of the IS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.4.2 Increasing privileges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.4.3 Lateralisation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.5 Actions on objective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.5.1 IS encryption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.5.2 Blackmail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.5.3 Speciﬁcity of Clop for TA505 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.6 Evasion methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.6.1 Use of compression codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.6.2 Use of signed binaries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.7 Attack infrastructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.8 Targeting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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3 Links with other attacking groups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1 Clients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1.1 Lazarus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1.2 Silence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2 FIN7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

145 Appendix: the Necurs botnet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.1 Return of the Necurs botnet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2 Massive distribution by Necurs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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6 Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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1 TA505 from 2014 to 2017
It would seem that the TA505 intrusion set goes back to at least 2014 but was only mentioned publicly for the ﬁrst
time on Twitter in 2017. Until 2017, its activity seems to have been conﬁned to the distribution of trojans andransomwares [1].

1.1 Malware distributed
1.1.1 Banking trojans
In terms of ﬁnal payload, TA505 has always widely used banking trojans that are not speciﬁc to it, such as Dridex
and Trickbot:

DridexTA505 is supposed to have distributed the Dridex malware [2] as of July 2014, i.e. one month after its creation(June 2014) [1]. Its use of speciﬁc ID botnets1 within the Dridex network of botnets, controlled by the Evil Corp
cybercriminal group, would suggest that TA505 was a Dridex affiliate from 2014 to 2017. ID botnets used by TA505
between 2014 and 2015 would have been botnet IDs 125, 220 and 223. The 220 botnet is thought to have contained
9650 bots in April 2015 [3], and mainly targeted banks [4], particularly in France. In 2016, TA505 is thought tohave mainly concentrated on the use of Locky ransomware, to the detriment of Dridex malware, then resumed
propagation of Dridex in 2017 through 7200 and 7500 ID botnets. TA505 ﬁnally stopped using Dridex in 2018 [5].

Fig. 1.1: Dridex Botnet IDs corresponding to TA505

1 The number attributed to the version of Dridex associated with a subset of bots it handles. These ID botnets are used to differentiate theactivity of each of its affiliates and associate different ID botnets with the same operator.

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TrickBot
TA505 is also thought to have been an affiliate of TrickBot2 , known under the pseudonym of mac1 [5]. The use of
TrickBot by TA505 only lasted a few months in 2017. For example, a campaign dating back to June 2017 targetedFrance and the United Kingdom [5].

1.1.2 Ransomware
2016 saw the appearance of Locky ransomware. Frequently used, it has targeted many victims. Like Dridex, Locky
works on the principle of affiliates [1].
According to Proofpoint, affiliate number 3 of Locky and the affiliate of ID botnet Dridex 220, TA505, have points
in common, such as similar lures on their phishing emails and very strong similarities regarding Javascript, VBScript
codes and Microsoft Word macros used [7]. There is also an absence of Dridex 220 campaigns concomitant with the
emergence of Locky [8]. Proofpoint [7] also pinpoints links between Locky and the affiliate of Dridex ID botnet
7200, TA505 at this time, comparing Dridex 2017 campaigns with Locky past campaigns [1]. TA505 is therefore
presumed to be affiliate number 3 (”Affid=3”) of this ransomware.
Although the main ransomware used by the group remains Locky, TA505 is thought to occasionally use other ransomwares (Bart3 , Jaff 4 , Scarab 5 , Philadelphia6 , GlobeImposter7 and GandCrab8 ).
Locky stopped operating in 2017.

1.2 Distribution and compromise methods
TA505 seems to have distributed its malware only through phishing email campaigns. This intrusion set was characterised by its massive use of Necurs botnet (see appendix in chapter 5) for the distribution of emails [9].
Comment: open source reports associate all ransomwares distributed by the Necurs botnet to TA505. However, some ofthese ransomwares were used over the same periods. It seems unlikely that TA505 operated as many encryption codesat the same time. It is more likely that Necurs had several clients simultaneously.
This intrusion set relies exclusively over that period on social engineering to run its payload contained in malicious
attachments linked to emails sent [9]. These attachments could be zip or 7zip archives containing VBS script orJavascript to be run by their victims, HTML pages containing malicious Javascript, or Offices documents bugged
with malicious macros.
Although TA505 does not seem to have used software vunerability to compromise its targets, it is interesting toobserve that it has kept up to speed with the latest social engineering techniques. It therefore distributed bugged
Office documents via the DDE mechanism less than a month after the potential abuse of this feature became
common knowledge [10].

2 Trickbot, which appeared in October 2016, and a derivative of Dyre, possibly operated by members of the Business Club until November 2015.

Reminder: the Business Club was responsible for JabberZeuS and GameOverZeuS(GoZ) malware. When the GoZ botnet was dismantled,
the Business Club is thought to have divided its activites between Dridex and Dyre malware. Trickbot could be operated by former membersof the Business Club, or by a copycat having acquired the source code of Dyre [6].
3 ransomware which was very limited during 2016.
4 ransomware active from May to June 2017.
5 Variant of the ﬁrst open-source Hidden Tear ransomware (published in 2015), used for the ﬁrst time by TA505 in June 2017.
6 Ransomware-as-a-Service available for 400 dollars on the Dark Web.
7 ransomware used from July to December 2017. 24 campaigns distributing GlobeImposter were found by Proofpoint in December 2017 [9,5]
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2 Development of TA505 since 2018
The year 2018 was a turning point in the attack methods of the intrusion set. TA505 gradually reduced its distribution of malicious banking codes and ransomwares to move into the distribution of backdoors.
However, this intrusion set does not seem to be content with running a payload on its victim’s computer. When it
deems it useful, TA505 tries to compromise the entirety of the information system (IS) it penetrated.
It also seems, in some cases, to resell accesses to the backdoors it has installed, which makes it difficult to distinguishbetween speciﬁc TA505 activities and those of potential clients.
The chain of attack described in this chapter corresponds to the activities that ANSSI believes are linked to theintrusion set.

2.1 Infection vector
The only infection vector currently known to be used by the TA505 intrusion set is phishing emails including a
malicious attachment or link. Until 2018, the intrusion set relied practically exclusively on the Necurs botnet to
distribute its payloads. However, following the unavailability of the botnet in January and February 2018, TA505
seems to have less often used its services [9].
This last point however is uncertain as there is little information on the alternative email distribution methodsof the intrusion set. Given that TA505 has often deployed an email credentials theft implant among its victims[11][12], it is possible that it accumulates email addresses to distribute its new phishing campaigns.
It has also been mentioned that some of its phishing emails had been distributed via machines infected by the
Amadey [11] malware. Given that TA505 also uses Amadey malware as indicated in section 2.3.1, it may have created its own Amadey botnet to distribute its malicious emails, or may use the services of an existing Amadey botnet.
This operating mode also usurps the recipient addresses of its emails, which makes it difficult to analyse its email
distribution infrastructure [13].

2.2 Social engineering
The intrusion set continues to rely on social engineering to run its malicious payloads on the machines of its email
recipients, using several formats for attachments to work around its targets’ security systems: .url [14], .iqy [9],SettingContent-ms [15], MS publisher ﬁles [16], .wiz and .pub [17], .iso [18]. The aim of these documents was often
to run msiexec9 commands via macros on the victim’s machine to upload and run a malware.
However, in the second half of 2019 and ﬁrst half of 2020, TA505 seems to have modiﬁed and stabilised its social
engineering scheme. It now sends an HTML page as an attachment containing malicious Javascript code. This code
redirects the victim towards an URL of a legitimate but compromised website.
This same URL corresponds to an HTML page containing a minimal Javascript code redirecting the victim towards
a page hosted by a machine controlled by the intrusion set. This page mimicks that of a legitimate ﬁle-sharing site
adapted to the target such as Onedrive, Dropbox [19] or Naver10 (during one of its campaigns in South Korea) [20].
The victim is then encouraged to download, open and enable VBA macros of an Office document, usually Excel,
containing a malicious payload .

9 Tool used to interact in command line with the installation, updating and de-installation engine of software speciﬁc to Microsoft operating

systems
10 Korean internet portal service.

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Fig. 2.1: Initial TA505 compromise method
The intrusion set gradually increases the complexity of its social engineering method. In October 2019, it is thought
to have directly sent links towards phishing pages in its malicious emails. It then used URL shorteners to mask thesemalicious links.
In late February 2020, it abandoned the URL shortener strategy and started to use HTML attachments with Javascriptwith redirection from a compromised site, which made it even more difficult to detect its emails. Furthermore, someof its redirection pages integrate a link towards iplogger.org, a service allowing the intrusion set to inspect IP addresses visiting these pages[21].
Finally, it has already been observed that the phishing pages of the intrusion set distributed empty Office documents
when a person other than the victim visited them. This behaviour can be explained by the fact that the intrusion
set ﬁlters the IP addresses to which it chooses to distribute its malicious documents or only distributes them within
limited time slots.

2.3 Initial compromise
TA505 has a varied attack arsenal to be deployed among its victims having run its malicious attachments. It consistsof codes available both publicly and commercially on the black market or which seem to be exclusive to it. It
therefore has malware development capabilites or ﬁnancial resources to obtain them. The intrusion set deploys its
arsenal in several stages and has different codes for each of them.

2.3.1 Stage 1 codes
The TA505 intrusion set seems to have tested several stage 1 codes11 . It brieﬂy used the following codes:
11 a stage 1 code is deﬁned here as an implant with limited features aimed at deploying a more sophisticated code and possibly rapidly performing

reconnaissance of the infected system to help the intrusion set determine if the victim and their IS are of interest.

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Development of the activity of the TA505 cybercriminal group• Quant Loader is a simple, low-cost downloader available on the black market. The intrusion set used it fromJanuary to April 2018 [9].
• Marap is a downloader that seems speciﬁc to the intrusion set. Athough it has a modular structure and aknown reconnaissance module, few attacks using this code have been documented and the intrusion set does
not seem to have used it since August 2018 [22].
• Amadey is a downloader available on the black market. This code is thought to have been used from April
to June 2019 by the intrusion set [23].
• Andromut, also known as Gelup, is a downloader that seems speciﬁc to the intrusion set. This code differsfrom the previous ones by setting up anti-analysis mechanisms. However, no occurrence of this code seems
to have been detected apart from in summer 2019 [24].
The TA505 intrusion set therefore does not seem to hesitate to discard some of its malwares in order to test others. Despite that, a trend does emerge: it seems to more regularly use the stage 1 malware Get2, whose backdoor
component is also called Friendspeak [13]. Since the ﬁrst publication of this malware in September 2019 [19], theintrusion set regularly uses it.
Get2 performs a basic reconnaissance of the machine it infects by sending to its C2 server information such as thename of the infected machine, the name of the user, the version of the Windows operating system and list of active
processes on the machine. In return, if the machine is deemed to be of interest, it receives the URL to which it can
upload the next stage malware.

Fig. 2.2: Timeline of the stage 1 codes used by TA505

2.3.2 Second-level codes
Once its stage 1 code has been deployed, the intrusion set can deploy several malwares.
• The FlawedAmmyy malware exists since 2016 and is built from the source code of the publicly disclosed
legitimate remote-administration tool Ammyy Admin. Although it has RAT12 features, FlawedAmmyy has
also been used by the intrusion set as a stage 1 code. The intrusion set is thought to have used it between
March 2018 and September 2019 [18]. FlawedAmmyy seems to be exclusively used by TA505 since 2018.
However, this backdoor is thought to have been used before this time period, when TA505 did not use thistype of code yet. It is therefore not entirely conﬁrmed that FlawedAmmyy is exclusive to TA505.
• The tRat malware was used by TA505 in October 2018 [16]. Little information is available about this door.
Modules need to be downloaded for the backdoor to acquire features, yet none of its modules have been
documented.
• Remote Manipulator System, also called RMS or RmanSyS, is a legitimate tool developed by the Russiancompany TEKTONIT, used for malicious purposes. This tool is available free of charge for non-commercial
purposes and corrupted versions are also available on the black market. TA505 is thought to have started to
deploy this tool from November 2018, and until June 2019 [25].
12 Remote Administration Tool

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Development of the activity of the TA505 cybercriminal group• The ServHelper backdoor comes in two [17] versions: one version acts as a stage 1 code, the other has RAT
features. The intrusion set is supposed to have used this backdoor over a period covering at least from November 2018 to August 2019 [18]. ServHelper does not seem speciﬁc to the intrusion set: several IT security researchers have observed attacks in which it was involved but also using methods and tools that are different
from those of TA505 [5][18][26].
• FlawedGrace, also known as Gracewire, is a backdoor with standard RAT features. It was mentioned forbeing used for the ﬁrst time by TA505 in December 2018 [17] and is thought to be still used by it in 2020 [27].
Like FlawedAmmyy, TA505 seems for the time being to be the only one to use this backdoor. However its
existence prior to 2018 makes it uncertain whether it was used by TA505 exclusively.
• The FlowerPippi backdoor was detected once in June 2019 [11]. This malware has basic RAT features and it
is also designed to be used as a stage 1 code by offering initial recognition of the infected system.
• SDBbot is a malware that seems to be speciﬁc to the intrusion set. Its ﬁrst use was probably September 2019[20] and the intrusion set has constantly used it since.

Fig. 2.3: Timeline of the stage 2 codes used by TA505

2.4 Compromising of the information system
Once its malwares are installed, the intrusion set can try to lateralise itself within a compromised network. Its goal
is to become the domain administrator. To achieve this, it uses several methods.

2.4.1 Exploration of the IS
The intrusion set scans the network to collect more information on the IS and discover vulnerable services [28].
One of the tools used by TA505 is the PowerSploit suite, a set of PowerShell scripts available in open-source andused to test the security of an IT network. The intrusion set particularly focuses on the Active Directory of the IS
and has already deployed in the past another penetration test tool, PingCastle, to test conﬁguration weaknesses
affecting that service.
Although crucial to take over the network, the intrusion set does not necessarily seem to perform these operations
ﬁrst. In several cases observed, the intrusion set ﬁrstly tends to try to compromise several other machines before
scanning the IS and the Active Directory.
The intrusion set seems to continue its network mapping work after having compromised the credentials of adomain administrator. It has already been observed that TA505 used a query software of Active Directory called
AdFind on a domain controller to fully map an IS of which it had become the domain administrator.
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2.4.2 Increasing privileges
The method preferred by TA505 to increase its privileges and lateralise throughout a network seems to be thecollection of credentials on compromised machines. The Mimikatz collection tool, available free of charge in opensource, is regularly used by the intrusion set and other tools of this type may also have been used. Unconﬁrmed
hypotheses have also been made on the use of MS17-010 vulnerability 13 by the intrusion set [28].

2.4.3 Lateralisation
To facilitate its lateralisation operations and increase its robustness within a compromised network, the intrusion
set has very frequently used Cobalt Strike, a penetration testing framework, and the TinyMet tool14 . However,TA505 also often uses native Window tools such as WMIC and RDP to run its malware on new machines by using
stolen credentials.

2.5 Actions on objective
2.5.1 IS encryption
The main goal of the intrusion set is to deploy ransomware. The use of ransomware by this intrusion set goes backto at least 2016 with its use of the Locky malware.
Major developments since 2018 can be explained by the fact that TA505 now seeks to use ransomware to compromise entities liable to pay a high ransom (big game hunting) and to encrypt all the machines of the compromisedIS.
During TA505-related attacks, Clop ransomware, also called Ciop, was deployed. This malware was observed forthe ﬁrst time in February 2019 [20]. It has no automatic propagation functions. Consequently, the intrusion set uses
some speciﬁc tools to deploy it within a whole IT system. Using a script, it deploys a malware, poorly documented inopen-source but until now systematically called « sage.exe » by the intrusion set, on several machines [28]. Thesemachines then connect to all the machines of the victim IS to successively run two payloads on each of them witha domain administrator account:• a malware called DeactivateDefender whose aim is precisely to disable Windows Defender [20][28];• the ransomware itself.
It is probable that TA505 relies on the network mappings performed during the gradual compromission of the IS
to choose the machines on which to run « sage.exe » and maximise the impact of its ransomware.
An occurrence of use of the Rapid ransomware by TA505 was also observed by the South Korean Financial Security
Institute (FSI) [20] in December 2019.

2.5.2 Blackmail
A website was created in March 2020 to publish exﬁltrated data of Clop ransomware victims not having paid theirransom, probably to increase pressure on future victims. A release was published by the attackers stating thatshould a hospital be accidentally victim of their ransomware, the data decrypter would be immediately provided.
If, as sugested in section 2.5.3, Clop is speciﬁc to TA505, this illustrates the capability of this intrusion set to follow
a trend initiated by other ransomware operators [29].
This trend is also interesting as it indicates that the intrusion set is required to exﬁltrate data of its victim’s IS. If suchdata were to exceed a certain volume, it is then probable that TA505 needs to deploy speciﬁc tools and infrastructure
for this task. Such things have not yet been observed for this intrusion set.
13 Critical vulnerability in the SMB service(Server Message Block) of Windows-run machines. This vulnerability was used during the WannaCry

international campaign in 2017.
14 This tool, freely available in open-source, is a particularly small loading code used to download and run the Meterpreter penetration testingtool.

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2.5.3 Speciﬁcity of Clop for TA505
ANSSI had mentioned a technical link between Clop ransomware and TA505. Indeed, Clop and FlawedAmmyy
had been signed by the same valid but malicious security certiﬁcate [30].
To this, it is possible to add that these two malwares were compiled in similar environments and modiﬁed at thesame time to change the letter « l » into « i » uppercase [20] in their chains. Furthermore, they have the samecharacteristic name « swaqp.exe » in separate attacks.
It therefore seems probable that one single intrusion set handles both codes. Given that TA505 is the only one tohave been seen to use them since 2018, it seems that both codes are speciﬁc to it.

2.6 Evasion methods
The intrusion set multiplies strategies to minimise the detection of its malware. Besides the use of attached document with unusual formats mentioned in section 2.2, TA505 has also used Excel 4.0 type macros. These very oldmacros were not often detected by security solutions during their adoption by the intrusion set. Likewise, TA505
relies heavily on native Windows tools, which require closer supervision of the IS to detect their malicious use.

2.6.1 Use of compression codes
TA505 uses a compression code15 to make it more difficult to analyse its malware. This code, called Minedoor [13],was used to compress both early stage malwares such as FlawedGrace, and ﬁnal codes deployed by TA505 such as
Clop or DeactivateDefender [31].
Although this compression code is a valuable way to monitor TA505’s arsenal, caution is required. Attacks using
codes protected by Minedoor with very different kill chains from that of TA505 have already been observed [13].
It therefore seems that this code is not speciﬁc to TA505.

2.6.2 Use of signed binaries
The intrusion set signs its malware by using legitimate but malicious security certiﬁcates. They often take overnames of existing businesses. TA505’s codes are therefore more difficult to detect [20].
Like the Minedoor malware, it is not certain that all the malware signed by the certiﬁcates used by TA505 are linked
to this intrusion set. Indeed it may be that TA505 used a third party to sign its codes and that this same third party
may reuse those certiﬁcates to sign the malware of other intrusion sets.

2.7 Attack infrastructure
As mentioned in section 2.1, the infrastructure used by the intrusion set to distribute its emails is not widely documented.
TA505 particularly seems to rent its infrastructure to conduct its operations, in particular to host its malicious Ofﬁce documents and for its Get2 C2 servers16 . The life cycle of this infrastructure is usually less than a month andthe intrusion set permanently generates new domain names. These domain names often consist of several words
separated by « - » and usually try to typosquat17 ﬁle-sharing services such as Onedrive ou Onehub for example.
TA505 is thought to use a different strategy for the C2 servers of its penetration tools such as TinyMet or Cobalt
Strike. It directly uses IP adresses as C2 servers and not domain names but still relies on a rented infrastucture.
15 Called packer.
16 Command and control servers: these machines are used to send instructions to malware and receive results.
17 Show strong similarities with another domain name for misleading purposes.

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Little information is available about the infrastructure compromised by TA505. Web servers compromised by the
intrusion set were analysed in February 2019 [20], indicating that several copies of the malicious web console Filesman had been found as well as a non-documented Linux backdoor.

2.8 Targeting
Although they only represent a fraction of the intrusion set’s real activity, the table below presents a set of campaigns conducted by TA505, documented in open-source since 2018.
PeriodTargeted geographical area

Targeted sector

SourceJanuary 2018

N/A

Automotive industry[14]

August 2018

N/A

Financial[22]

September-October 2018

N/A

Financial[32]

November 2018

N/A

Financial
Retail[17]

December 2018

N/A

Financial
Retail[17]

November-December 2018

United States

Food industry
Distribution
RetailCatering

[33]
[34]

December 2018 – March 2019

Chile, India, Italia, Malawi,
Pakistan, South Africa,
South Korea, China,
United Kingdom, France, United States

Financial
Hospitality[25]

February 2019

South Korea

N/A

[20]

April 2019

N/A

Financial[35]

April 2019

Chile, Mexico, Italia, China,
South Korea, Taiwan

N/A

[23]

June 2019

United Arab Emirates, South Korea,
Singapore, United States,
Saudi Arabia, Morocco

N/A

[11]

June-July 2019

United States, Bulgaria, Turkey, Serbia,
India, Philippines, Indonesia

Banks

[19]
[18]
[11]

June 2019Japan, Philippines, Argentina

N/A

[11]

July-August 2019

Saudi Arabia, Oman

Government agency[18]

July-August 2019

TurkeyGovernment agency
Education[18]

September 2019

Canada, United States

N/A

[19]

September 2019

Greece, Singapore,
United Arab Emirates, Georgia,
Sweden, Lithuania

Financial

[19]
[18]
[36]
[11]

United Kingdom, France, United States

Financial,
Healthcare,
Retail,Education
Research[19]

October 2019

December 2019

South Korea

N/A

[20]

December 2019

Germany, Netherlands

Education[37]

January-March 2020

United States

Pharmaceutical
Healthcare
Retail[27][19]

The ﬁnancial sector used to be the exclusive target of the intrusion set before 2018 and has remained a regulartarget since.
TA505 has however gradually expanded its victim proﬁle to other new sectors.
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From a geographical point of view, all the continents are targeted by this intrusion set. A point of interest is the
special attention TA505 seems to pay to South Korea. This interest could be linked to the fact that the intrusion set
could have been working in connection with the Lazarus intrusion set as mentioned in chapter 3.

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3 Links with other attacking groups
3.1 Clients
Given its varied arsenal, the broadness of its targets, its sometimes massive, sometimes targeted campaigns, TA505
could well be a hacker-for-hire i.e. a provider of IS compromise and access qualiﬁcation services. Its clients will
provide it with a list of potential targets which TA505 will try to compromise, to then sell these compromised or
qualiﬁed accesses to clients.
At least two potential clients have been identiﬁed by editors: the Lazarus intrusion set known to be tied to North
Korean interests in open-sources and the Silence [38] group.

3.1.1 Lazarus
The simultaneous presence of Lazarus and TA505 has already been observed by different sources. In early January
2018, the Vietnamese CERT issued an alert relating to attacks targeting the ﬁnancial sector, combining indicatorsof compromise attributed to intrusion sets linked to North Korean interests in open-sources to others attributed toTA505 [39]. According to Lexfo, IOCs found simultaneously on bank networks and Powershell scripts, attributed toTA505 and to Lazarus, seem similar [40].
In addition, the speciﬁc targeting of South Korea by TA505 could indicate an order from a ﬁnal client such as an
intrusion set known to be linked in open-sources to North Korean interests.

3.1.2 Silence
There are code and infrastructure links between FlawedAmmyy and Truebot (aka Silence.Downloader), a remote administration tool speciﬁc to Silence18 . According to the Group-IB editor, FlawedAmmyy.downloader
and Truebot were developed by the same individual [41]. Furthermore, Silence is thought to have attacked at least
one bank in Europe via TA505 in order to compromise its IS [42].
Comment: If Silence does indeed call on TA505 for the initial compromise, it would be to change the TTPs, as Silence,from its beginning, in 2016, is autonomous in the sending of phishing emails and initial compromise.

3.2 FIN7
According to the Korean Financial Security Institute (FSI) [20], there are similarities between TA505 and the FIN7
cybercriminal group, the successor to Carbanak and now specialising in the theft of credit card information. The
two groups are thought to:• share the IPs of joint C2 servers ;• use FlawedAmmyy, Cobalt Strike and TinyMet (BabyMetal for FIN7);• use batch script for internal recognition purposes;• be lateralised through the RDP protocol and PSExec;• use Shim Database (SDB) in the same way. This particularity is also highlighted by Proofpoint [19].
Comment: FIN7 and TA505 could in fact be working together. It seems that the FSI observed that an infection chain inline with those of TA505 deployed malware targeting POS terminals (PoS systems), belonging to FIN7.

18 Russian-speaking cybercriminal group specialising in compromising ATMs for fraudulent cash withdrawals [38].

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4 Conclusion
Despite the scale of its activity as an affiliate of Dridex and Locky, TA505 was only identiﬁed as such in 2017, atthe same time as its ﬁrst uses of backdoors.
Often mistaken for the Evil Corp cybercriminal group (operating the Dridex botnet and BitPaymer ransomware),and sometimes considered to be the operator of the Necurs botnet, TA505 uses a scalable attack arsenal which it
implements in varied and sometimes simultaneous campaigns, casting confusion over its motives. As such, the ties
it has with Lazarus and Silence suggest that TA505 conducts parallel campaigns for its own behalf and campaigns
for its clients.
The scale of its campaigns since 2019 and its targeting of several sectors in France, make this intrusion set a threatof special concern in 2020.

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5 Appendix: the Necurs botnet
5.1 Return of the Necurs botnet
The Necurs botnet (alias CraP2P) ﬁrst appeared in 2011 [43].
Two known botnet modules are:• spam, used for example:– during pump and dump campaigns (especially relating to cryptoassets) as in March 2017;– in 2018, when Necurs acquired a new module .NET spamming [44]);– between 2016 and 2017, when Necurs propagated the Kegotip banking Trojan through The Uprateloader and The Rockloader19 , (Loader used to recover email addresses available in hard disks and touse them in future spam campaigns [46];– after the dismantling of the Kelihos botnet in 2017, when Necurs was thought to have retrieved some ofits business, in particular consisting of dating spam.
• proxy/DDoS (addition of the DoS module in February 2017) [3].
The Necurs botnet communicates with its operators in different ways [47]:• Its main communication network consists of a list of IP addresses and static hard-coded domains in the sampling of Necurs malware;• If this method is not capable of obtaining an active C2, Necurs uses its domain generation algorithm (DGA):
the main DGA produces 2048 C2 domains every 4 days. When Necurs operators record a DGA domain to
inform bots of the existence of a new C2, the domain does not indicate the real IP address of the C2. This IP
address is obfuscated with an encryption algorithm. All the domains are tried out until one of them matches
and replies using the right protocol;• If this method also fails, the C2 domain is recovered on the P2P network.
Furthermore, the C2 infrastructure is divided into three levels. The last is the C2 backend. In this way, an infected
system communicates with at least two layers of the C2 proxy when it is trying to communicate with the C2 backend.
The ﬁrst C2 layer consists of cheap private virtual servers located in countries like Russia or the Ukraine whereas
the second layer is usually hosted in Europe, sometimes Russia. There are thought to be 11 Necurs botnets, i.e. 11
C2 backends, tightly controlled by one single group [4]. Four of these botnets represent 95% of all infections [47,48].

5.2 Massive distribution by Necurs
From 2016 to 2019, Necurs was the most frequently used method to deliver spams and malware for cybercriminals,
and responsible for 90% of malware distributed by email worldwide. 1 million systems were infected in 2016 rising
to 9 million on 10 March 2020 [48].
Between 2016 and 2017, Necurs mainly distributed Locky, Jaff (copy cat of Locky, GlobeImposter, Philadelphia,
Lukitus and Ykcol (variants of Locky) and Scarab ransomware, as well as Dridex and TrickBot banking Trojans.
As of August 2018, Necurs started to roll out phishing campaigns targeting ﬁnancial institutions, while continuing
its massive propagation of (FlawedAmmyy, Quant Loader, AZOrult, ServHelper) malware, a majority of which
belongs to TA505’s arsenal.
In 2020, Necurs lost clients to Emotet, which replaced it in the distribution of Dridex and TrickBot [49], and distributed massive get-rich-quick spam campaigns. Its daily infections are mainly located in India, Indonesia, Iran,
19 Loader used during compromises to propagate Locky, Dridex 220, Pony and Kegotip ransomware [45].

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Mexico, Turkey, Vietnam and Thailand. 4892 infections have been located in France. [47, 48].
TA505 is thought to have massively distributed malware via the Necurs botnet, to such an extent that it is possiblethat the group actually operates this botnet, or at least is very closely tied to its real operator.
Comment: although it is possible that TA505 and the operator of the Necurs botnet have been mistaken for each other,
it appears that the open-source tends to attribute all campaigns propagated by Necurs to TA505 through to at least late2017 (pump-and-dump spam campaigns and other frauds being excluded), whereas it is a gigantic botnet probably usedby cybercriminal groups other than TA505. Indeed, users of remote-controlled botnets, are often capable of renting out
access to segments of their botnet on the black market to send DDoS, span campaigns etc.

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6 Bibliography[1]

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[21]

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[23]

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BitSight. Joint Effort with Microsoft to Disrupt Massive Criminal Botnet Necurs. Mar. 10, 2020. URL: https ://www.bitsight.com/blog/joint-effort-with-microsoft-to-takedown-massive-criminal-botnetnecurs (visited on 04/24/2020).

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[49]

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- 20/08/2020
Open License (Étalab - v2.0)
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